Polynitrobenzofluorides and the method of preparation thereof



United States Patent 3,417,153 POLYNITROBENZOFLUORIDES AND THE METHOD OF PREPARATION THEREOF Don N. Gray, Josef J. Schmidt-Collerus, and Claibourne D. Smith, Denver, Colo., assignors to the United States of America as represented by the Secretary of the Air Force No Drawing. Filed Apr. 26, 1961, Ser. No. 127,759 17 Claims. (Cl. 260-646) The present invention concerns the novel polynitrobenzofluorides and halopolynitrobenzofluoride compositions and the methods for the preparation thereof.

Due to the thermal sensitivity of trinitrotoluene and related compounds an extreme need has been felt in this art by the military departments as well as industry in general in recent years for more thermally stable explosive compositions.

Thus it is an object of our invention therefore to provide a novel explosive composition exhibiting increased thermal stability. It is the further object of this invention to provide a thermally stable explosive composition without the loss of explosive strength. Likewise it is an object of our invention to provide an explosive composition having improved impact stability.

We have discovered that 2,4,6-trinitrobenzofluorides have a considerably higher thermal stability than do nonfluorinated compounds such as trinitrotoluene. It has also been found that contrary to theoretical expectation trinitrobenzofluorides have a higher explosive strength and a better impact stability than non-fluorinated compounds such as trinitrotoluene.

Prior to the present invention trinitro-alpha trifluorotoluene 2,4,6-trinitrobenzotrifluoride had not been isolated. The analog 2,4,6-trinitrobenzotrichloride was reported by Ganguly (Ben, 1925, 58, 708). Thus it was contemplated that the 2,4,6-trinitrobenzotrichloride could be prepared by Gangulys method and converted into the corresponding trifluoro material by metathetical exchange With anhydrous hydrogen fluoride. However, in a number of attempts Gangulys work could not be repeated.

In another series of attempts to prepare trinitrobenzotrifluoride, 3 -hydroxy-2,4,6-trinitrobenzotrifluoride was converted via its pyridine salt into the 3-chloro-derivative with phosphorus. It was envisioned that the halo-2,4,6- trinitrobenzotrifluoride such as 3-chl0ro-2,4,6-trinitrobenzotrifluoride could be readily reduced with copper powder and ethanol water by a method similar to that used for the preparation of 1,3,5-trinitrobenzene from picryl chloride as disclosed by Desvenques in Chem. at Ind., Volume 25, Page 291, (1931). However, under these conditions the starting material was recovered quantitatively.

The polynitrobenzofluorides produced by this inventio are represented by the general formula OzN NO2 N 02 The intermediate halopolynitrobenzofluoride compounds are represented by the general formula In the foregoing formulas R is a radical selected from the group consisting of a fluorine substituted alkyl, a fluorine substituted aryl and a fluorine substituted alkylene group containing from 1 to 18 carbon atoms and F is a number of fluorine atoms varying from 1 to 3, X is represented by fluorine, chlorine, bromine or iodine.

The aforesaid fluorine substituted alkyl group is illustrated by, but not limited to, radicals selected from the group comprising methyl, ethyl, propyl, butyl, octyl, decyl, octadecyl, etc.

The aforesaid fluorine substituted aryl group is illustrated by, but not limited to, radicals selected from the group comprising phenyl, benzyl, naphthyl, anthryl, phenanthryl, etc.

The aforesaid fluorine substituted alkylene group is i1- lustrated by, but not limited to, radicals selected from the group comprising ethylene, propylene, butene, isobutylene, pentent, decene, etc.

One method of synthesizing the aforesaid fluorine compounds comprises the reaction of a hydroxy-2,4,6-trinitrobenzotrifluoride, such as 3-hydroxy-2,4,6-trinitrobenzotrifluoride with pyridine, or phosphorus pentachloride, isolating the product formed thereby and reacting said product with phosphorus oxychloride, phosphorus oxybromide, phosphorus oxyfluoride, phosphorus oxyiodide, carbonyl bromide, carbonyl fluoride or phosgene, which yields the halopolynitrobenzotrifluoride.

The reduction of the halopolynitrobenzotrifluoride can be effected with hydroiodic acid (H1) or the reaction product of an alkali metal iodide compound illustrated by, but not limited to, the group consisting of sodium iodide, potassium iodide, lithium iodide and an organic aliphatic monocarboxylc acid containing from 2 to 10 carbon atoms. The molar ratio of the alkali metal iodide to the carboxylic acid can vary from 10 to 1 to 0.1 to 1. The actual molar quantity of the alkali metal iodide compound should always be at least equal to the molar quantity of the halopolynitrobenzotrifluoride.

To effect the reduction of a halopolynitrobenzotrifluoride it is dissolved in suflicient quantity of a liquid aliphatic ketone containing from 3 to 8 carbon atoms illustrated by, but not limited to, acetone, methyl, methyl ethyl ketone, methyl-i-propyl ketone, hexanone, etc. Alternatively the halopolynitrobenzotrifluoride can be dissolved in suflicient quantity of an aliphatic monocarboxylic acid containing from 2 to 8 carbon atoms illustrated by, but not limited to, acetic acid, propanoic acid, valeric acid, heptanoic acid or hexanoic acid.

The reduction is then effected by the addition of hydroiodic acid or the aforementioned reaction products and allowing these reactants to remain at room temperature for 10 hours or heating at C. for 1 hour. The preferred temperature range is 25-100 C. After this period the reaction mixture is poured into a large quantity of water containing material which will reduce the iodine formed in the reaction. The olynitrobenzotrifluoride deposits as a brown oil and is collected and purified by crystallization or column chromatography.

The reduction of the halopolynitrobenzodifluorides and monofluoridcs can be effected in an analogous manner with the same reactants.

All of the foregoing reactions can be carried out in the presence of an adequate quantity of benzene or other aromatic or aliphatic hydrocarbons such as the aforesaid alcohols or ketones.

The 3-chloro-2,4,6-trinitrobenzotrifluoride may also be prepared by the reaction of 3-hydroxy-2,4,6-trinitrobenzotrifluoride with phosphorus pentachloride directly at temperatures of between 50l50 C. and isolating the product by pouring into water and filtering the product.

3 Example 1 The 3-hydroxy-2,4,6-trinitrobenzotrifluoride was prepared by the following method:

Hydroxybenzotrifluoride (60 g.) was dropped into nitric acid (180 ml.) at the rate of 20 drops per minute at room temperature without cooling. Nitrogen oxides were evolved. Near the end of the addition the product began to crystallize. Next a mixture of fuming acid ml.) and concentrated sulphuric acid (40 ml.) was added and stirring continued for another hour. The whole was then poured on ice and the solids were filtered off. After drying in air the compound was recrystallized by adding hexane to its alcoholic solution, to give pale yellow crystals. These yellow crystals were positively identified as 3-hydroxy-2,4,6-trinitrobenzotrifluoride.

Pyridine (7.9 g., 0.1 mole) was added to S-hydroxy- 2,4,6-trinitrobenzotrifluoride (29.7 g., 0.1 mole) in 95% ethyl alcohol (200 ml.). The salt was precipitated as large yellow crystals, M.P. 179-180".

The pyridine salt (37.6 g., 0.1 mole) was suspended in sodium-dried benzene (50 ml.) to which phosphorus oxychloride (15.3 g., 0.1 mole) was then added. After 2 hours refluxing the now homogeneous solution was washed with cold water and evaporated, to give a slight yellow solid. Recrystallization from 95 alcohol yielded the chloro-compound as white needles which were positively identified as 3-chloro-2,4,6-trinitrobenzotrifluoride.

The 3 chloro 2,4,6 trinitrobenzotrifluoride crystals were dissolved in dry acetone (40 ml.) and added to sodium iodide (24 g.) and glacial acetic acid (8 ml.) in dry acetone (80 ml.) and the whole was refluxed for 3 hours, then cooled and poured into cold aqueous sodium sulphite (10 g. in 200 ml.), a brown oil being precipitated. The water-acetone layer was decanted and crushed ice (50 g.) was added to the oil. After several minutes stirring the oil solidified and was dissolved in hot 95% alcohol. Crystallization occurred after addition of several drops of water and the crystals were filtered off. After drying under a vacuum at room temperature for 6 hours, the material was recrystallized from benzene three times to yield white crystals. These white crystals were identified by conventional methods of organic qualitative analysis to be 2,4,6- trinitrobenzotrifluoride.

Example 2 Phosphorus pentachloride (20.8 g., 0.1 mole) was added to 3-hydroxy-2,4,6-trinitrobenzotrifluoride (29.7 g., 0.1 mole) in 95% isopropyl alcohol (200 ml.). The salt was precipitated as large yellow crystals, M.P. 179-180".

The chloride salt thereby produced was suspended in sodium-dried benzene to which phosgene (9.8 g., 0.1 mole) was then added. After 2 hours refluxing the now homogeneous solution was washed with cold water and evaporated, to give a slightly yellow solid. Recrystallization from 95 alcohol yielded the chloro-compound as white needles. These white needles were identified as 3-chloro- 2,4,6-trinitrobenzotrifluoride.

The 3-chloro-2,4,6-trinitrobenzotrifluoride (15.7 g.) was added to hydroiodic acid (10 g.) in dry methyl ethyl ketone (100 ml.) and the whole was refluxed for 3 hours, then cooled and poured into cold aqueous sodium sulphite (10 g. in 200 ml.), a brown oil being precipitated. The water-acetone layer was decanted and crushed ice (50 g.) was added to the oil. After several minutes stirring the oil solidified and was dissolved in hot 95% alcohol. Crystallization occurred after addition of several drops of water and the crystals were filtered off. After drying under a vacuum at room temperature for 6 hours, the material was recrystallized from benzene three times, to yield white crystals. The white crystals were identified as 2,4,6-trinitrobenzotrifluoride.

The polynitrobenzotrifluoride produced by the foregoing method can be used as an explosive either alone or in mixture with the earth metals such as exemplified by, but not limited to, aluminum. The Weight ratio of polynitrobenzotrifluoride to aluminum can vary from 10 to 1 to l to 10.

Comparative testing of polynitrobenzotrifluorides The heat sensitivity of the explosive developed-by this invention were tested and compared with the heat sensitivity of trinitrotoluene according to the method set forth by Henkin and McGill in Ind. and Eng. Chem, 44, 1391 (1952). By this method the explosion temperature designated as the cook off temperature of a particular explosive is determined by exposing the said explosive to a high temperature bath for varying lengths of time until detonation occurs. This testing procedure for trinitrotoluene and trinitrobenzotrifluoride yielded the following 7 Temp.=Degrees Centigrade; Time expressed in 1/120 second.

These comparative tests show that trinitrobenzotrifluoride is considerably less heat sensitive than its nonfluorinated analog, trinitrotoluene.

Explosive strength tests The Trauzl test, specifications for which were estab lished by international convention, has been widely used in the explosives industry. In the standard test 10 grams of explosive and a detonator are placed in a central cavity in a cylindrical block of lead, and sand is tamped down on top to cover the charge prior to firing. After the shot, the volume of the enlarged cavity is measured and the net expansion due to the explosion is computed. The figure of merit is taken as the ratio of the net expansion for the explosive to that for 10 grams of a standard explosive (TNT).

The feasibility of this test for comparison of explosive strength has been demonstrated by the detailed investigation carried out by Gordon et al., Ind. and Eng. Chem. 47, 1794 (1955). It has been shown by these authors that the Trauzl block provides an acceptable figure of merit for equal weights of various explosives. The relationship between weight of explosive (w) and the volume of expansion (v can be expressed by the equation:

where a and b are constants relating the charge weight with energy.

When TNT is chosen as the standard explosive, and value for a and b are determined for this particular explosive, then experimental data for other explosives can be fitted to the TNT curve by a suitable choice of a constant k and expressed in the following equation:

where a and 17 represent the constants found experimentally for TNT.

The values for a and b for TNT were determined from a least-mean-squares curve obtained from the data given for this explosive.

Data for other explosives will fall on the same curve when the appropriate k value is used. Hence the k value is a true figure of merit for any given explosive, including metallized explosives.

k Value for explosives tested kValue 2,4,6-trinitrotoluene 1.00 2,4,6-trinitrobeirzotrifluoride 1.17

Mixture of 2,4,6-trinitrobenzotrifluoride and 28 mesh powdered aluminum (90/10 weight ratio of trinitrobenzotrifluoride to aluminum) 1.30

These k values show that the trinitrobenzotrifluoride has approximately 17% greater explosive strength than does its non-fluorinated analog. These tests also demonstrate the relative explosive strength of a mixture of trinitrobenzotrifluoride and aluminum.

Having described various embodiments of the novel polynitrobenzotrifluorides, methods for preparing same and explosive compositions embodying the said polynitrobenzotrifluorides.

We claim:

1. An explosive composition consisting essentially of a polynitrobenzofluoride of the general formula:

wherein R is selected from the group consisting of a fluorine substituted alkyl, a fluorine substituted aryl and a fluorine substituted alkylene radical containing from 1 to 18 carbon atoms and n is a number from 1 to 3.

2. An explosive composition consisting essentially of a trinitrobenzodifluoride.

3. An explosive composition consisting essentially of a trinitrobenzomonofluoride.

4. A chemical intermediate composition consisting essentially of a halopolynitrobenzofluoride of the general formula:

a polynitrobenzotrifluoride of the general formula:

OzN NO2 wherein R is a fluorine substituted alkl group having from 1 to 18 carbon atoms and n is a number from 1 to 3 carbon atoms.

9. An explosive composition consisting essentially of 2,4,6-trinitrobenzotrifluoride.

10. A method of producing a halopolynitrobenzofluoride of the general formula:

OzN NO2 wherein R is selected from the group consisting of a fluorine substituted alkyl, a fluorine substituted aryl and a fluorine substituted akylene radical containing from 1 to 18 carbon atoms and n is a number from 1 to 3, X is selected from the group consisting of chlorine, bromine, fluorine and iodine, by reacting a 3-hydroxy-polynitrobenzofluoride compound with a compound from the group consisting of pyridine and phosphorus pentachloride, isolating the product thereof, reacting the said product with a strong halogenating agent to produce a halopolynitrobenzotrifluoride.

11. A method of producing a polynitrobenzotrifluoride by reducing a halopolyn-itrobenzotrifluoride with a compound from the group consisting of hydroiodic acid and the reaction product of an alkali metal iodide with an aliphatic mono-carboxylic acid containing 2 to 8 carbon atoms and recovering a polynitrobenzotrifluoride as the product of said reaction.

12. The method of claim 11 wherein the halopolynitrobenzotrifluoride is dissolved in a ketone containing from 3 to 8 carbon atoms.

13. The process of claim 12 wherein the halopolynitrobenzotrifluoride as reacted with sodium iodide and acetic acid, and recovering the trinitrobenzotrifluoride product by precipitation.

14. The process of producing 2,4,6-trinitrobenzotrifluoride by reacting 3-hydroxy-trinitrobenzotrifluoride with pyridine, recovering the pyridine salt and reacting same with phosphorus oxychloridle to yield 3-ch1oro- 2,4,6-trinitrobenzotrifluoride, recovering the 3-chloro-trinitrobenzotrifluoride and reacting said 3-chloro-2,4,6-trinitrobenzotrifluoride with sodium iodide and acetic acid, thereafter precipitating ofl the product 2,4,6-trinitrobenzotrifluoride.

15. The process of producing 3-chloro-2,4,6-trinitrobenzotrifluoride by reacting 3-hydroxy 2,4,6-trinitrobenzotrifluoride with phosphorus pentachloride at a temperature in the range of 50150 C. and isolating the 3- chloro-2,4,6-trinitrobenzotrifluoride.

16. The process of reacting 3 -chloro -2,4,6 trinitrobenzotrifluoride with hydroiodic acid to yield 2,4,6-trinitrobenzotrifluoride wherein the molar ratio of hydroiodic acid to 2,4,6-trinitrobenzotrifluoride is greater than 1.

17. The process of producing 2,4,6-trinitrobenzotrifluoride by reacting 3-hydroxy-2,4,6-trinitrobenzotrifluoride with phosphorus pentachloride at a temperature of approximately 50 C., isolating the 3-chloro-2,4,6-trinitrobenzotrifluoride, reacting said 3-chloro 2,4,6-trinitrobenzotrifluoride with a member from the group consisting of hydroiodic acid and the reaction product of an alkali metal iodide with a monocarboxylic acid containing from 2 to 8 carbon atoms.

References Cited UNITED STATES PATENTS 1,397,826 11/1921 Hayange 149-37 2,600,678 6/ 1952 ONeill 149-37 2,988,438 6/1961 Allovio 149-37 2,088,912 8/1937 Lange et al. 260-646 2,519,317 8/1950 Kolka et a1 260-646 2,733,275 1/ 1956 Revallier 260-646 2,257,093 9/1941 Friedrich et a1 260-646 2,179,605 11/1939 Wesson 260-646 X LELAND A. SEBASTIAN, Primary Examiner.

US. Cl. X.R. 149-105 

1. AN EXPLOSIVE COMPOSITION CONSISTING ESSENTIALLY OF A POLYNITROBENZOFLUORIDE OF THE GENERAL FORMULA:
 11. A METHOD OF PRODUCING A POLYNITROBENZOTRIFLUORIDE BY REDUCING A HALOPOLYNITROBENZOTRIFLUORIDE WITH A COMPOUND FROM THE GROUP CONSISTING OF HYDROIODIC ACID AND THE REACTION PRODUCT OF AN ALKALI METAL IODIDE WITH AN ALIPHATIC MONO-CARBOXYLIC ACID CONTAINING 2 TO 8 CARBON ATOMS AND RECOVERING A POLYNITROBENZOTRIFLUORIDE AS THE PRODUCT OF SAID REACTION. 